Abstract
Quantum optical technology provides an opportunity to develop new kinds of gravity sensors and to enable novel measurement concepts for gravimetry. Two candidates are considered in this study: the cold atom interferometry (CAI) gradiometer and optical clocks. Both sensors show a high sensitivity and long-term stability. They are assumed on board of a low-orbit satellite like gravity field and steady-state ocean circulation explorer (GOCE) and gravity recovery and climate experiment (GRACE) to determine the Earth’s gravity field. Their individual contributions were assessed through closed-loop simulations which rigorously mapped the sensors’ sensitivities to the gravity field coefficients. Clocks, which can directly obtain the gravity potential (differences) through frequency comparison, show a high sensitivity to the very long-wavelength gravity field. In the GRACE orbit, clocks with an uncertainty level of 1.0times 10^{-18} are capable to retrieve temporal gravity signals below degree 12, while 1.0times 10^{-17} clocks are useful for detecting the signals of degree 2 only. However, it poses challenges for clocks to achieve such uncertainties in a short time. In space, the CAI gradiometer is expected to have its ultimate sensitivity and a remarkable stability over a long time (measurements are precise down to very low frequencies). The three diagonal gravity gradients can properly be measured by CAI gradiometry with a same noise level of 5.0 {mathrm{mE}/sqrt{mathrm{Hz}}}. They can potentially lead to a 2–5 times better solution of the static gravity field than that of GOCE above degree and order 50, where the GOCE solution is mainly dominated by the gradient measurements. In the lower degree part, benefits from CAI gradiometry are still visible, but there, solutions from GRACE-like missions are superior.
Highlights
The determination of a precise gravity field model is essential for a variety of geoscience applications, such as monitoring global sea level rise, refining ocean circulation models, realizing a global height reference system, understanding the Earth’s geodynamics and so on (Pail et al 2015)
We followed the conceptual design of a space-based cold atom interferometry (CAI) gradiometry mission that was accomplished by Trimeche et al (2019)
We evaluated the performance of the one- and three-arm CAI gradiometry for determining the Earth’s gravity field
Summary
The determination of a precise gravity field model is essential for a variety of geoscience applications, such as monitoring global sea level rise, refining ocean circulation models, realizing a global height reference system, understanding the Earth’s geodynamics and so on (Pail et al 2015). It was proposed to measure gravity gradients using spatially separated interferometers with free falling atoms (Snadden et al 1998). This instrument is fundamentally different from other types of gradiometers as its proof masses are individual atoms (clouds of atoms) rather than precisely machined macroscopic objects. It has a long-term stability, less affected b√y drifts, and achieves a sensitivity level of a few√tens of E/ Hz on ground (Sorrentino et al 2014) or 3 E/ Hz (Asenbaum et al 2017).
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have